Eclipse Observation Tips
The spectacular sight of a total solar eclipse is for most of us a once-in-a-lifetime event. Unless you're an astronomer or an avid eclipse follower, you'll probably get just one chance to see it. It's estimated that only one in a thousand people ever experiences totality. This wondrous spectacle of the complete halo around the Sun can't be seen under any other earthly circumstances. In addition to the sight of the corona, there are other marvelous phenomena to observe during a total eclipse. The daytime darkness and the swift onset of the Moon's shadow add to the drama of the few short minutes the corona is visible. Shadow bands, Baily's beads, the reaction of plants and animals -- all add to the excitement and impact of the inexorable alignment of Sun, Moon, and Earth. It's simply a matter of being in the right place at the right time -- and knowing what to look for.
Selecting an Observation Site
The partial phases of a total solar eclipse are usually visible over a wide area. But only within the path of totality can you see the spectacular and striking effects. The difference between experiencing a total eclipse and a partial eclipse is, literally, "the difference between night and day." Those who live within the path or take the opportunity to travel there have the chance to be rewarded with one of the most fleeting and beautiful visions of Nature's grandeur.
Your choice of a site within the path should be guided by three main factors:
(1) Duration of totality at the site
(2) Unobstructed view of the Sun
(3) Chances for clear skies
First of all, you need to be located within the path of totality during the time of the eclipse in order to be able to see the corona. For any given locale within the path of totality, a point nearer the central line of the eclipse has more time in totality; this is because the Moon's shadow, which forms an ellipse on the surface of the Earth, is wider nearer the center of the path. If you are located just within the path, totality will not last very long -- less than a minute. However, the "edge phenomena" of a total eclipse (Baily's beads, diamond-ring effect, and view of the chromosphere) will last longer there.
To ensure an unobstructed view of the eclipse, you need to know approximately where the Sun will be in the sky. You don't want any trees or mountains, for example, blocking your view. An easy way to find this out is to look for the Sun from your vantage point a day or two before the eclipse at the same time of day totality occurs. This will tell you if anything is in your way. Also, if you're on a hill or tall building with a good view of the west, you may get a chance to see the approach of the Moon's shadow as it races toward you over the Earth.
The third factor in choosing a site is the weather. Unless you fly above the clouds to observe an eclipse, you'll always have to take some risk on the weather. But there is a lot you can do to optimize your chances to see the eclipse. The meteorological term for cloudy skies is "sky cover." It is measured in numbers from 0 to 10, with each number representing a tenth. (For example, a sky cover of 3 indicates 30% overcast, or 70% clear.) Weather Bureau records will show the average sky cover for different places along the path at the time of year of the eclipse.
However, sky cover predictions are only general estimates covering large areas. Local weather conditions can be very different for places a short distance apart. You'll want to avoid places likely to have fog; also, stay away from mountain ridges where clouds tend to gather. But perhaps the greatest asset in finding clear skies for an eclipse is mobility. Driving a few miles to a clearer ******** at the last minute could save the day for you.
Observation Safety Precautions
The total phase of a solar eclipse, when the sky is dark and the corona is visible around the Sun, is a beautiful sight. The best way to observe the event during these few brief minutes is simply to look directly at this glimmering halo in the sky. The corona is a million times fainter than the bright disk of the Sun; there is no danger of eye damage when looking directly at the corona or the prominences during totality. Binoculars may reveal even finer detail, but most observers agree that the naked eye is the best "instrument" for viewing the full glory of the event.
For about an hour before and after the total phase the Sun is only partially obscured. This is when it is dangerous to look directly at the Sun. Normally the Sun is too bright to look at anyway. But during the partial phases, the Sun does not appear as bright, and you may be tempted to look directly at it. DON'T DO IT! The danger of damaging your eyes does not depend on brightness. As long as any portion of the Sun's disk remains visible it can still cause eye damage.
The lenses of your eyes act as tiny magnifiers; if you look at the partially eclipsed Sun, its rays are focused on the retina of your eyes and can burn them. This is the same sort of thing that happens when you use a magnifying glass to focus the Sun to a pinpoint on paper or leaves to burn a hole in them. The only difference is that it is your eyes that would be burned. Part of the danger lies in the fact that the retina is not sensitive to pain; you wouldn't even feel it happening. But a retinal burn is permanent and irreversible, producing a blank spot in the most vital part of your field of vision.
Astronomers observe the sun directly through professionally manufactured optical filters that screen out the hazardous rays of the Sun. In recent years, manufacturers have also made available to consumers various forms of "eclipse viewers" that use the similar optical-grade filter material to give your a protected view of the crescent Sun during the partial phases.
And you're taking a big chance if you try to improvise your own filter. During the March 7, 1970, eclipse in the United States there were 145 reported cases of people who damaged their eyes by looking at the partially eclipsed Sun either directly or through sunglasses, exposed film, smoked glass, and the like. None of these homemade devices can be guaranteed safe. Play it smart and don't take any chances with your precious gift of vision.
Safe Viewing Techniques
There are two safe ways to observe the partial phases of a solar eclipse. One way is to purchase a professionally manufactured solar filter (or "eclipse viewer") from a reputable source. These viewers are made with optical-grade filters that are designed to protect your eyes from damage by the visible and infrared wavelengths of the Sun.
The other way, with does not involve looking directly at the Sun, is to viewing the image of the Sun projected onto some surface; the image can be focused by having the sunlight pass through a pinhole. This is the same effect seen when the light from the partially eclipsed Sun shines through the leaves of a tree, creating tiny crescent images in the shadow on the ground. The diagram below illustrates how to build and use a simple pinhole projector. This is the safe and recommended way to observe the passage of the Moon across the face of the Sun during the partial phases of a solar eclipse. (If the eclipse is televised, it would also be safe to view it on the TV screen.) And don't forget: during the few minutes of totality it's OK to look directly at the Sun's corona.
Here is a checklist for observing an eclipse covering site selection criteria and observation equipment, followed by a list of phenomena in complete sequence for a total solar eclipse.
_____ Site near center of path for maximum time of totality
_____ First contact (eclipse begins)
_____ Second contact (totality begins)
_____ Third contact (totality ends)
_____ Fourth contact (eclipse ends)
_____ Unobstructed view of Sun
_____ Provisions for last-minute mobility
_____ Pinhole projector or safe solar filters
_____ Binoculars (FOR TOTAL PHASE ONLY)
_____ Cameras, film, etc.
First Contact (Eclipse begins)
_____ Moon begins to cover Sun
_____ Crescent images of Sun
_____ Gradual darkening
_____ Shadow bands (2 or 3 minutes before totality)
_____ Baily's beads (1/2 minute before totality)
_____ Diamond ring effect
_____ Approach of shadow from the west
Second Contact (Totality begins)
_____ Stars and planets
_____ Darkness of landscape
_____ Plant/animal reactions
_____ Temperature drop
Third Contact (Totality ends)
_____ Darkness passes
_____ Diamond ring effect
_____ Baily's beads
_____ Shadow bands
_____ Gradual lightening of sky
_____ Crescent images of Sun
_____ Gradual uncovering of Sun
Fourth Contact (Eclipse ends)